Bicycle wheels

ABSTRACT

A wheel for use with a bicycle includes a hub for mounting the wheel to a bicycle, a rim about which a tire is mountable, and a plurality of spokes that extend between the hub and the rim. The rim and/or one or more of the spokes have a leading and/or trailing edge, at least part of which has an undulating configuration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application patent Ser. No.13/809,615, filed on Jan. 11, 2013, now U.S. Pat. No. 9,610,800 issuedon Apr. 4, 2017, which is a National Stage of PCT/GB2012/050166, filedon Jan. 26, 2012, which claims priority to and the benefit of U.S.Provisional Application Patent Ser. No. 61/530,087, filed on Sep. 1,2011, GB Application Patent Serial Nos. 1101417.2 and 1112995.4, filedJan. 27, 2011 and Jan. 28, 2011, respectively, the entire disclosure ofeach being hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to improvements in bicycle wheels, and inparticular to a bicycle wheel having an improved rim configuration.

BACKGROUND

Conventional bicycle wheel rims are manufactured from straight extrudedsections of material, such as metal, which are cut, bent into a hoopshape and the ends bonded, welded or otherwise joined together.Alternatively, the wheel rims may be formed from a composite materialsuch as carbon fibre reinforced plastic. Such rims are made directlyinto a hoop shape and so the above bending step is not required. In bothof the above arrangements, the rim has a constant depth at all pointsaround its perimeter. Spokes are then connected to various points aroundthe radially inner surface of the wheel rim. Alternatively, the bicyclerim and spokes are formed integrally from composite materials.

In use, conventional wheel rims may suffer aerodynamic problems. Forexample, conventional wheel rim designs may result in a large amount ofdrag on the wheel, reducing the speed of the bicycle. Furthermore,movement of ambient air, travelling at a non-zero yaw angle relative tothe general direction in which the bicycle is travelling, may cause atransverse resultant force to be applied to the wheel. If this force isapplied at a location forward or rearward of the hub, the force willcreate a moment about the center of the wheel, which, in the case of thefront wheel, will act to cause the wheel to steer away from the desiredpath. The rider must apply a steering input to counteract this. Thepoint of action of this force on the wheel is known as the center ofpressure. In particular, the center of pressure is defined as the pointat which the moment about the vertical and horizontal axes in the planeof the wheel is zero (i.e. zero yaw and zero roll). This point is notapplicable at zero yaw since the side force is effectively zero.

SUMMARY

In a first aspect A new bicycle wheel has now been devised whichovercomes or substantially mitigates some or all of the above-mentionedand/or other disadvantages of the prior art.

It has been found that having leading and/or trailing edges of the rim,and/or one or more of the spokes, with an undulating configurationprovides aerodynamic advantages, in use.

Hence, according to a first aspect of the invention, there is provided awheel for use with a bicycle, the wheel comprising a hub about which thewheel is mountable to a bicycle, a rim about which a tire is mountable,and a plurality of spokes that extend between the hub and the rim,wherein the rim and/or one or more of the spokes have a leading and/ortrailing edge, at least part of which has an undulating configuration.

In some embodiments, the rim has a radially inner edge, at least part ofwhich has an undulating configuration.

Computational Fluid Dynamics (CFD) analysis has been carried out whichcompares the drag produced at 15 m/s on a wheel having a rim with anundulating configuration, with that produced on a wheel having aconventional, non-undulating rim. The speed of 15 m/s is chosen becauseit is close to the racing speed achieved by high level cyclists. Theresults show reduced drag in the case of the wheel having an undulatingrim at a range of yaw angles.

The undulating configuration may be smooth in form. For example, theundulating configuration may be substantially devoid of angulartransitions, or entirely devoid of angular transitions, between thepeaks and troughs of the undulating configuration. The undulatingconfiguration may be arranged along the full extent of the edge, suchthat the edge is either intermittently undulating or, most preferably,continually undulating. The peaks and troughs of the undulatingconfiguration may be arranged at regular intervals, or irregularintervals.

The radially inner edge with an undulating configuration preferably hasa radial distance that varies between the peaks and troughs of theundulating configuration. The radially inner edge may be continuallyundulating. In these arrangements, the radially inner edge may comprisea series of alternating concave and convex regions, which areimmediately adjacent to each other. In presently preferred embodiments,each peak of the undulating configuration has a convex exterior profile,in the plane of the wheel. There may be at least three pairs of peaksand troughs along the radially inner edge of the rim, more preferablytwelve and most preferably at least twenty-four.

The radially inner edge may have a regular arrangement of undulations,which have the same height, or alternatively alternate between two ormore different heights, where height is defined as the radial heightrelative to an annular base portion of the rim. The difference in radialheight between the peaks and troughs of the undulations is preferably atleast 5 mm, more preferably at least 10 mm, and most preferably at least20 mm.

One or more of the spokes may also have an undulating configuration, atleast on the leading and/or trailing edges. This undulatingconfiguration preferably has the features described above in relation tothe radially inner edge of the rim.

In other embodiments, one or more of the spokes may have a leadingand/or trailing edge, at least part of which has an undulatingconfiguration. This may be in addition to, or as an alternative to, anundulating configuration on a radially inner edge of the rim.

In these embodiments, the undulating configuration may be smooth inform. For example, the undulating configuration may be substantiallydevoid of angular transitions, or entirely devoid of angulartransitions, between the peaks and troughs of the undulatingconfiguration. The undulating configuration may be arranged along thefull extent of the edge, such that the edge is either intermittentlyundulating or, most preferably, continually undulating. The peaks andtroughs of the undulating configuration may be arranged at regularintervals, or irregular intervals.

One or more of the spokes may have a regular arrangement of undulations,which have the same height, or alternatively alternate between two ormore different heights, where height is defined as the radial heightrelative to an annular base portion of the rim. The difference in radialheight between the peaks and troughs of the undulations is preferably atleast 5 mm, more preferably at least 10 mm, and most preferably at least20 mm.

Preferably, the one or more spokes has both a leading edge and atrailing edge and at least part of both leading and trailing edges hasan undulating configuration. In preferred embodiments, the one or morespokes has a substantially oval or elliptical cross-section.

The rim preferably has side surfaces that meet at a radially inner edgeof the rim. The side surfaces preferably have a smooth configuration,and are most preferably generally convex in form. In particular, theside surfaces may curve laterally outwards from the base of the rim, andthen curve laterally inwards, before meeting at the radially inner edgeof the rim. The separation of the lateral edges of the rim may begreater than the separation of the lateral edges of a tire attached toit, for at least part, and preferably the majority, of the rim's depthin the plane of the wheel.

The radially inner edge of the rim, with an undulating configuration, ispreferably inwardly spaced from the lateral edges of the rim, and may begenerally centrally aligned between the lateral edges of the rim, i.e.,substantially aligned with a central plane of the wheel. In someembodiments, especially on a rear wheel, the radially inner edge of therim may be offset, to counteract the unequal tension experienced by thespokes due to unequal “dishing”. The radially inner edge is preferablyrounded so as to form a smooth convex curve in a plane orthogonal to theplane of the wheel. The side surfaces are preferably configured suchthat the radial inner edge is defined by rounded inner portions of theside surfaces. The exterior cross-sectional profile of the side surfacesat the radial inner edge of the rim preferably has a radius of at least5 mm, and most preferably at least 10 mm.

CFD analysis was carried out on a wheel having this rounded, radialinner edge configuration, with and without undulations according to theinvention, which compared the location of the center of pressure atdifferent yaw angles. The analysis showed that, at the yaw angles 0°,5°, 10°, 15° and 20°, the center of pressure was located closer to thehub in the case of the wheel having a rim with an undulatingconfiguration than in the case of the wheel having a conventional,non-undulating rim. Thus, the wheel having a rim with an undulatingconfiguration does not experience as great a force causing the frontwheel to yaw than the wheel having a conventional rim. This means therider need not apply as large a steering input to counteract the effectsof this force.

The undulating configuration may be smooth in form, with the radiallyinner edge of the rim comprising a series of alternating concave andconvex regions, which are immediately adjacent to each other. However,it has been found that aerodynamic advantages are also provided by anarrangement in which the rim has an annular base portion and a pluralityof projecting portions, at least an end portion of which has a graduallyreducing width in at least the plane of the wheel, and an angular apexat which a spoke may be mounted. In particular, in these arrangements,the radially inner edge of the rim may comprise a series of concaveregions, in the plane of the wheel, which are immediately adjacent toeach other and separated by an angular apex.

It has also been found that this configuration of projecting portionsoffers advantages when at least some of the projecting portions act assupport portions for the spokes of the wheel. In particular, it has beenfound that the support portion for each spoke may reduce the stressexperienced in the rim at the point at which the spoke is mounted.Hence, at least some of the projecting portions preferably definesupport portions for the spokes of the wheel.

According to a further aspect of the invention there is provided a wheelfor use with a bicycle, the wheel comprising a hub about which the wheelis mountable to a bicycle, a rim and a plurality of spokes that extendbetween the hub and the rim, wherein the rim has an annular base portionand a support portion for each spoke that projects from the baseportion, at least an end portion of each support portion having agradually reducing width in at least the plane of the wheel, to an apexat which the spoke is mounted.

The support portion for each spoke will typically project radiallyinwardly from the base portion, or approximately radially in the casewhere the spokes are connected to each side of the hub, e.g., in a crosspattern.

The wheel according to this aspect of the invention is advantageousprincipally because the support portion for each spoke reduces thestress experienced in the rim at the point at which the spoke ismounted. This means that a smaller quantity of material, or a lightermaterial, may be used to manufacture a wheel having the same strength asa conventional wheel, thereby reducing the weight of the wheel andpossibly also manufacturing costs. Alternatively, a wheel may bemanufactured having the same weight as conventional wheels, but withgreater strength for the weight.

The support portion for each spoke is preferably shaped to reduce theconcentration of stresses in the material of the rim relative to a spokemounted to a surface having a constant radial position, i.e., a uniformradial surface. Each support portion preferably has a height, i.e., thedistance the support portion projects relative to the base portion, thatis at least 10%, more preferably at least 20%, and most preferably atleast 25%, of the width of support portion at its base. Each supportportion preferably projects at least 5 mm relative to the base portion,more preferably at least 10 mm, and most preferably at least 20 mm.

The width of the support portion in the plane of the wheel may reduce ata constant rate, in at least the region of the apex. The profile of thesupport portion in the plane of the wheel may therefore be generallytriangular or trapezoidal, in at least the region of the apex.Alternatively, the width of the support portion reduces at an increasingrate, in the plane of the wheel. In particular, the support portion mayhave a convex profile, in the plane of the wheel, to each side of theapex, i.e., generally dome-shaped. In presently preferred embodiments,however, the width of the support portion reduces at a decreasing rate,in the plane of the wheel. In particular, the support portion may have aconcave profile, in the plane of the wheel, to each side of the apex.

The support portion for each spoke may also have a gradually reducingwidth in other planes aligned with the longitudinal axis of spoke. Theshape of the support portion for each spoke may therefore have agenerally conical configuration. The support portion will typically havea greater width in the plane of wheel, relative to other planes alignedwith the longitudinal axis of spoke, and may therefore have across-section in a plane perpendicular to the longitudinal axis of thespoke that is generally elliptical in shape.

The profile of the support portion is preferably smooth, at least in theplane of wheel. The support portion may have a width, in at least theplane of the wheel, that reduces continuously between the base portionand the apex at which the spoke is mounted. In particular, the radiallyinner surface of the support portion is preferably at an angle of morethan 90 degrees to the longitudinal axis of the spoke at all positionsbetween the base portion and the apex at which the spoke is mounted.

Each support portion may have a width at its base that is substantiallyequal to the separation between the spokes at the rim, such that thesupport portions are disposed immediately adjacent to one another.Alternatively, each support portion may have a width at its base that isless than the separation between the spokes at the rim, such that eitherthe base portion of the rim or other formations are interposed betweensupport portions of adjacent spokes on the radially inner surface of therim.

The rim may include ancillary formations interposed between the supportportions that are adapted to provide aerodynamic advantages, asdiscussed in more detail below. These formations may include projectionshaving a similar form to the support portions. Most preferably, however,these formations have a convex profile in the plane of the wheel, andare preferably generally dome-shaped, for example with a cross-sectionin a plane perpendicular to the longitudinal axis of the spoke that isgenerally elliptical in shape.

The apex of each support portion preferably has an end surface to whichthe spoke is either connected, or integrally formed. In the case wherethe spokes are separate components from the rim, the apex of the supportportion is preferably fastened to the end of the spoke. Alternatively,the spokes may be formed as part of the same component as the rim, andhence formed integrally therewith.

In presently preferred embodiments, there is a substantially smoothtransition between the surfaces of the support portion and the adjacentsurfaces of the spoke, for example such that there is substantially noshoulder formed between the support portion and the spoke. This is mostpreferably achieved by integrally forming the rim and the spokes bymolding, for example in composite material. However, in someembodiments, a small shoulder may be present. The shoulder is preferablyless than 15 mm, and most preferably about 10 mm or less, or about 8 mmor less, from the spoke. The end surface defined by the support portionin these embodiments, between the spoke and the shoulder, preferably hasan area that is less than 50% of the cross-sectional area of the base ofthe support portion, i.e., the interface with the annular base portionof the rim. The area of the end surface is more preferably less than 30%of the base of the support portion, and most preferably less than 20%.

Where the spokes are formed as separate components that are fastened tothe rim, the spokes are preferably attached to the associated supportportions by a suitable fastener. The fastener may be adapted to put thespoke under tension when assembled. Conventional fasteners extendthrough an aperture in a wall of the rim, with an enlarged head beinglocated to the radially outer side of the wall of the rim, and athreaded connector being located to the radially inner side of the wallof the rim, to which the spoke is connected. Where this type of fasteneris used, the apex of the support portion may include an aperture inwhich the fastener is mounted, as discussed above. In thesearrangements, it is also preferred that there is a substantially smoothtransition between the surfaces of the support portion and the adjacentsurfaces of the spoke, for example such that there is substantially noshoulder formed between the support portion and the spoke.

An alternative arrangement for fastening the spokes to the rim comprisesspokes that extend through an aperture in the wall of the rim and areretained by virtue of the spoke having an enlarged head located on theradially outer side of the wall of the rim. A further alternative isthat the spokes may be adhesively bonded to the rim.

Each support portion preferably has a single spoke that is aligned with,or approximately aligned with, a central axis of the support portion. Inparticular, the spoke may extend from the center of an end surface ofthe support portion. In an alternative arrangement, each support portionsupports two spokes, the spokes preferably connecting to opposite sidesof the hub. The support portion is preferably symmetrical, in at leastthe plane of the wheel, most preferably about a longitudinal axis of thespoke. Alternatively, the support portion can be non-symmetrical aboutthe plane of the wheel, and in particular offset to one side. This canbe useful in applications were the wheel spokes require unequal tensionon one side of the wheel compared to the other, or in cases where otherbenefits are provided by this arrangement.

The annular base portion of the rim preferably has a constant radialheight, and hence represents a minimum radial height of the rim, fromwhich the support portions, and any other formations, project. Theradial height of the annular base portion may be greater than the radialheight of the support portions, relative to the base portion.

The hub may have a conventional form, being adapted to be rotatablymounted to the frame of a bicycle. Typically, the hub will define aprojection to each side of the wheel, which is rotatably mounted to theframe. For example, the hub may comprise a cylindrical projection toeach side of the wheel, which is rotatably received within correspondingopenings in the frame. The spokes may be connected to the hub bysuitable fastening arrangements, or formed integrally with the hub.Commonly, the hub defines connection points for connection to thespokes, which may take the form of openings within which fasteners forthe spokes are located. In some embodiments the hub includes a centralmember having a substantially cylindrical form. The central member maybe provided with raised flanges, to which the spokes are connected.

The rim may define a radially outer surface adapted to retain a tire.The radially outer surface typically defines a circumferential channeladapted to receive a tire, which may have a generally U- or V-sectionshape. The circumferential channel may be defined by annular supportflanges, which project from each side edge of the radially outersurface. The rim may be formed from metal, or molded compositematerials.

The spokes are preferably elongate in form, and arranged to provideappropriate connection between the hub and the rim for the nature of thebicycle to which the wheel will be mounted. The spokes may be formed ofmetal, plastics or composite material, and may have the form of rods,blades or aerodynamic sections.

The wheel will typically have three or more spokes, for example twelve,sixteen or more. Where twelve or more spokes are provided, the spokesare preferably separate components that are mounted at one end to thehub of the wheel, and at the other end to a support portion. Typically,the spokes are formed or molded separately in metal, a compositematerial or other suitable material, and then assembled onto the rim andhub by bonding, welding or riveting, or joined using other methods orcombinations of them to form a one piece structure. However,particularly where the bicycle is intended for time trial racing, thewheel may have less than twelve spokes, for example three, four, five orsix spokes. In these arrangements, the spokes are preferably integrallyformed with the hub and rim of the wheel, for example by molding ofcomposite materials.

In order to reduce weight, the rim is typically hollow, with radiallyinner and outer walls, connecting side walls, and a chamber definedthere between. In some embodiments, the rim may include a reinforcingcore material, such as polymer foam, wood such as balsa, or anotherinternally reinforcing core material. The wheel preferably includes atire mounted to the radially outer surface of the rim. The tire istypically inflatable, and removable from the rim when deflated. Thepresent invention is suitable for use with a wide variety of differenttypes of bicycle, including racing bicycles and leisure bicycles.

According to a further aspect of the invention, there is provided abicycle having at least one wheel as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described in greater detail, byway of illustration only, with reference to the accompanying drawings,in which:

FIG. 1 is a side view of a first embodiment of a wheel according to theinvention;

FIG. 2 is a front view of the wheel of FIG. 1;

FIG. 3 is a perspective view of the wheel of FIGS. 1 and 2;

FIG. 4 is a cross-section through the rim of the wheel of FIGS. 1 to 3;

FIG. 5 is a side view of a second embodiment of a wheel according to theinvention;

FIG. 6 is a front view of the wheel of FIG. 5;

FIG. 7 is a perspective view of the wheel of FIGS. 5 and 6;

FIG. 8 is a perspective view of a third embodiment of a wheel accordingto the invention;

FIG. 9 is a side view of a fourth embodiment of a wheel according to theinvention;

FIG. 10 is a front view of the wheel of FIG. 9;

FIG. 11 is a perspective view of the wheel of FIGS. 9 and 10

FIGS. 12A-12D show side views of two conventional wheels, and two wheelsaccording to the invention, which underwent CFD analysis;

FIGS. 13A-13D show the exterior cross-sectional profile of the rim ofeach wheel of FIGS. 12A-12D.

FIG. 14 shows the CFD analysis data for the wheels of FIGS. 12 and 13;

FIG. 15 illustrates the CFD analysis data of FIG. 14 relating to thedrag forces across a range of yaw angles; and

FIG. 16 illustrates the CFD analysis data of FIG. 14 relating to thelocation of the center of pressure across a range of yaw angles.

DETAILED DESCRIPTION

The first With reference to FIG. 1, a bicycle wheel is generallydesignated 1. The wheel 1 has an annular rim 2, elongate spokes 3 and acentral hub 4.

The rim 2 has the form of a circular annulus. The rim 2 defines radiallyinner 5 and radially outer surfaces as well as side surfaces 7, 8. Theinner surface 5 defines the inner periphery of the rim 2, i.e. it facesinwardly, towards the central hub 4. The outer surface defines the outerperiphery of the rim 2, i.e. it faces outwardly, away from the hub 4.

The side surfaces 7, 8 of the rim 2 are symmetrical about the plane inwhich the wheel 1 lies, as shown in FIG. 4. In particular, the sidesurfaces 7, 8 are each curved in a plane orthogonal to that in which thewheel 1 lies, and are generally convex in form. They meet at a point onthe inner surface of the rim 2, in particular, at a radially inner edge11 of the rim. The side surfaces 7, 8 curve laterally outwards fromouter peripheries 12 of the side surfaces 7, 8 of the rim 2, and thencurve laterally inwards, before meeting at the radially inner edge 11 ofthe rim 2. The side surfaces 7, 8 have a smooth configuration.

A substantially V-shaped annular channel is provided in the outerperiphery of the rim 2, within which a tire 6 is received.

The hub 4 comprises an elongate cylinder 13. Two flanges 14 are providedon the cylinder 13, one close to each end of the cylinder 13. Each spoke3 connects to one of the flanges 14 at connection locations on theoutward-facing surface of the flange 14. These connection locations arespaced at regular intervals around the flange 14. Connection formationsare provided at these locations which are adapted to connect tocorresponding connection formations provided on the spokes 3. The spokes3 are elongate metal rods. In the embodiment shown in FIGS. 1 to 3,there are twelve spokes in total. Six of the spokes are connected to oneof the flanges 14, and six are connected to the other flange 14, in analternating arrangement.

As noted above, the flanges 14 are located close to, but not at, theends of the cylinder 13. This means that end portions 15 of the cylinder13 project from the wheel 1 and are adapted to rotatably mount the wheel1 to the frame of a bicycle.

The inner surface 5 of the rim 2 defines a plurality of elevations.These include support elevations 9, which are located in the region ofconnection of each spoke with the inner surface 5. Each supportelevation 9 connects to a spoke 3. The elevations also include ancillaryelevations 10, which are located between the support elevations. Bothsupport 9 and ancillary 10 elevations have a generally dome-shapeconfiguration. The support elevations 9 and the ancillary elevations 10cooperate to provide a regularly undulating inner surface of the rim102. When the wheel 1 is viewed from the side, as shown in FIG. 1, itcan be seen that the support elevations 9 are slightly raised relativeto the ancillary 10 elevations.

A second embodiment of a wheel according to the invention is shown inFIGS. 5 to 7, which is generally designated 201. FIG. 5 shows a bicyclewheel 201 having a rim 202 and hub 204. The rim 202 has radially inner205 and outer 206 surfaces, and side surfaces 207,208. As with the firstembodiment, the inner surface 205 defines the inner periphery of the rim202, i.e., it faces towards the central hub 204. The outer surface 206defines the outer periphery of the rim, i.e., it faces outwardly, awayfrom the hub 204.

As with the first embodiment, the side surfaces 207, 208 are symmetricalabout the plane in which the wheel 201 lies. The side surfaces 207, 208are curved in a plane orthogonal to that in which the wheel 201 lies,such that they meet at an annular edge on the inner surface 205 of therim 202.

In the example of FIGS. 5 to 7, there are four wide spokes 216. Thespokes connect the inner surface 205 of the rim 202 to the hub 204. Thespokes 216 connect to the inner surface 205 at equally spaced locationsalong the length of the inner surface 205.

Equally spaced recesses 210 are defined in the portions of the innersurface 205 which are located between the points of connection of theinner surface 205 to the spokes 203. These recesses 210 define a seriesof undulations, such that, when the wheel is viewed from the side as inFIG. 5, a continuous profile of elevations 211 and recesses 210 is seen.The heights H1, H2 of the elevations alternate between two slightlydifferent values along the length of the inner surface, as can be seenin FIG. 5. As discussed above in relation to the first embodiment, thisregularly undulating inner surface of a rim 202 has been found toprovide aerodynamic advantages.

The hub 204 shown in FIGS. 5 to 7 comprises a circular disc which isoblate, ie the thickness of the disc is greater at its central regionthan at its periphery. The hub 204 has curved side surfaces which meetat an annular edge at the periphery of the disc, giving the disc acigar-shaped cross-section. The hub 204 further defines a central shaft218 projecting outwardly from the side surfaces of the hub 204. Theshaft 218 is adapted to be rotatably mounted to the frame of a bicycle,for example by being received within corresponding openings in theframe.

The spokes 216 connect to the hub 204 at points that are equally spacedabout the periphery of the disc.

A third embodiment of a wheel according to the invention is shown inFIG. 8, which is generally designated 301. This differs from theembodiment shown in FIGS. 5 to 7 in that undulations 319 are alsodefined on the spokes 316. In particular, the undulations 319 aredefined on the long edges of the spokes 316 which lie in the plane ofthe wheel 301. The undulating surface of the spokes 316 has also beenfound to provide aerodynamic advantages.

A further embodiment of a wheel according to the invention is shown inFIGS. 9 to 11, which is generally designated 101.

The inner surface of the rim 102 defines recesses 110 at regularintervals along its length. The presence of the recesses 110 means thatthe inner surface 105 defines a plurality of support elevations 111,each having an angular apex. The profile of the support elevations 111of the present embodiment is steeper than the profile of the elevations9, 10 shown in FIG. 3.

Such support elevations 111 are located on either side of each recess110. The support elevations 111 are therefore also spaced at regularintervals along the length of the inner surface 105 of the rim 102. Whenthe wheel 101 is viewed from the side, as shown in FIG. 9, each recess110 is symmetrical about a line drawn through the hub 104 and bisectingthe two adjacent support elevations 111.

In this embodiment, the recesses 110 in the rim 102 are deeper than inthe first embodiment. In addition, the support elevations 111 do notcurve smoothly but instead have an angular apex. Furthermore, each ofthe elevations on the inner periphery of the rim is connected to a spoke103.

In this embodiment, the support elevations 111 offer the advantage ofreducing the stress experienced in the rim 102 at the point at which thespoke 103 is mounted.

Each spoke 103 connects one of the flanges 114 to the apex of one of thesupport elevations 111. A connection formation is provided at the apexof each support elevation 111. This connection formation is adapted toconnect to a corresponding connection formation provided on the spoke103. In the example shown in FIGS. 9 to 11, each elevation 111 isconnected to the opposite flan to its neighboring support elevations111.

In use, the weight of the frame and rider passes through the hub 104 ofeach of the bicycle's wheels 101. This places stress on the wheel 101and, in particular, on regions of the rims 102 in the vicinity of thepoints at which the spokes 103 connect to the inner surface 105 of therims 102. Owing to the claimed configuration of the wheel, the stressesexperienced in those regions are less than those experienced incorresponding regions of wheels 101 that do not have such aconfiguration.

The support elevation 111 for each spoke 103 reduces the stressexperienced in the rim 102 at the point at which the spoke 103 ismounted. This means that a smaller quantity of material, or a lightermaterial, may be used to manufacture a wheel having the same strength asa conventional wheel, thereby reducing the weight of the wheel andpossibly also manufacturing costs. Alternatively, a wheel may bemanufactured having the same weight as conventional wheels, but withgreater strength.

FIG. 12 shows side views of two conventional wheels, and two wheelsaccording to the invention, which underwent CFD analysis. Wheels (a) and(d) have conventional, non-undulating rims. Wheel (c) has substantiallythe same configuration as the embodiment of the invention shown in FIGS.1 to 4. Wheel (b) has substantially the same configuration as theembodiment of the invention shown in FIGS. 9 to 11. The exteriorcross-sectional profile of each rim is shown in FIG. 13. Wheels (a) and(c) have profile with a greater thickness along the majority of itsradial extent, and a radially inner edge with a more rounded form,relative to Wheels (b) and (c). However, each of wheels (a) to (d) hasthe same number of spokes and the same hub configuration. Furthermore,all spokes present in wheels (a) to (d) have the same cross-section.This ensures that any differences in results in the CFD analysis resultsbetween the wheels are caused by the different rim configurations ratherthan different spoke or hub configurations.

Computational Fluid Dynamics (CFD) analysis was carried out on thesewheels, at a speed of 15 m/s, and at yaw angles of 0°, 5°, 10°, 15° and20°. The data for the lift, drag and side forces, the torque, and thecenter of pressure for each wheel, at each yaw angle, are set out inFIG. 14.

FIG. 15 illustrates the CFD analysis data of FIG. 14 relating to thedrag forces across the range of yaw angles tested. Wheels (a) and (c)have the same cross-sectional shape, with the only difference being theundulating configuration of the radially inner edge of Wheel (c). TheCFD data shows that at all of the yaw angles tested, the wheel with theundulating configuration, Wheel (c), has less drag than the wheel withthe conventional, non-undulating configuration, Wheel (a). Similarly,Wheels (b) and (d) have the same cross-sectional shape, with the onlydifference being the undulating configuration of the radially inner edgeof Wheel (b). The CFD data shows that at yaw angles of 0-10° at least,the wheel with the undulating configuration, Wheel (b), has less dragthan the wheel with the conventional, non-undulating configuration,Wheel (d). The CFD data also shows that the least drag is achieved byWheel (c), which has an undulating configuration in combination with amore rounded, radially inner edge.

FIG. 16 illustrates the CFD analysis data of FIG. 14 relating to thelocation of the center of pressure across a range of yaw angles.Typically, the closer the center of pressure to the hub, the less forcecausing the front wheel to yaw experienced by the rider. This means therider need not apply as large a steering input to counteract the effectsof this force. The CFD data shows that the wheels that have a morerounded, radially inner edge. Wheels (a) and (c) have a center ofpressure that is consistently a short distance to the front of the hubacross the range of yaw angles tested. Of those wheels, the CFD datashows that at all of the yaw angles tested, the wheel with theundulating configuration, Wheel (c), has a center of pressure that iscloser to the hub than the wheel with the conventional, non-undulatingconfiguration, Wheel (a), across the range of yaw angles tested.

What is claimed is:
 1. A wheel for use with a bicycle, the wheelcomprising: a hub for mounting the wheel to a bicycle; a rim about whicha tire is mountable; and a plurality of spokes extending between the huband the rim, wherein at least part of a radially inner edge of the rimhas an undulating curve configuration, the undulating curveconfiguration having peaks and troughs, and wherein the radially inneredge has convex profiles in convex regions of the rim, the convexregions including the peaks.
 2. The wheel as claimed in claim 1, whereinthe undulating curve configuration is arranged along the full extent ofthe rim, such that the rim is either intermittently undulating orcontinually undulating.
 3. The wheel as claimed in claim 1, wherein thepeaks and the troughs of the undulating curve configuration are arrangedat regular intervals.
 4. The wheel as claimed in claim 1, wherein therim comprises concave regions and the convex regions that alternate,such that a first of the concave regions is immediately adjacent to afirst of the convex regions.
 5. The wheel as claimed in claim 1, whereinthe undulating curve configuration has the convex profiles in a plane ofthe wheel, such that the peaks do not comprise an angular apex.
 6. Thewheel as claimed in claim 1, wherein the undulating curve configurationhas the convex profiles in a plane of the wheel, such that the convexregions do not comprise a region of constant radial distance.
 7. Thewheel as claimed in claim 1, wherein the rim comprises side surfaces,and an exterior cross-sectional profile of the side surfaces at theradially inner edge of the rim has a radius of at least 5 mm.
 8. Thewheel as claimed in claim 1, wherein a difference in radial heightbetween the peaks and the troughs is at least 5 mm, at least 10 mm, orat least 20 mm.
 9. The wheel as claimed in claim 1, wherein the rim hasside surfaces that curve laterally outwards from outer peripheries ofthe side surfaces of the rim, and then curve laterally inward, beforemeeting at the radially inner edge of the rim.
 10. The wheel as claimedin claim 1, wherein the undulating curve configuration has a radius thatvaries between the peaks and the troughs of the undulating curveconfiguration, and wherein at least a subset of the peaks of theundulating curve configuration are points of minimum radius of theundulating curve configuration.
 11. The wheel as claimed in claim 1,wherein the undulating curve configuration has a radius that variesbetween the peaks and the troughs of the undulating curve configuration,and wherein the troughs of the undulating curve configuration are pointsof maximum radius of the undulating curve configuration.
 12. A bicyclehaving at least one wheel as claimed in claim
 1. 13. The wheel of claim1, wherein each of the convex profiles is a same size and shape.
 14. Thewheel of claim 1, wherein a first subset of the convex profiles has afirst radial height relative to a radially outer edge of the rim, and asecond subset of the convex profiles has a second radial height relativeto the radially outer edge of the rim, and wherein the first radialheight is greater than the second radial height.
 15. The wheel of claim14, wherein the plurality of spokes are attached to the rim at theconvex regions corresponding to the first subset of the convex profiles.